• 한국응용과학기술학회지
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• 제28권3호
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• pp.367-373
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• 2011

This research is a basic researching process for producing solid fuel that mixing paper sludge and Heat Transfer Medium Oil. Under the presence of Heat Transfer Medium Oil, paper sludge is heated and dried with home appliance microwave for comparing drying efficiency and energy efficiency of different types of drying method. As a result, Heat Transfer Medium Oil and paper mixing case of drying method, OMD, is the most efficient way to shorten the time for evaporating moisture in the paper sludge. In addition, heat transfer effect and density is increased with adding Heat Transfer Medium Oil by microwave. Future more, OMD's energy cost for evaporating whole moisture is 78% cheaper than MD. Also, OMD process shows the best energy efficiency with comparing other process. Evaporation rate of paper sludge evaporation process with microwave is 11.66% increased by adding Heat Transfer Medium Oil 150g. Preheating Heat Transfer Medium Oil or improving different ways injecting Heat Transfer Medium Oil is a good way to increase a rate of initiative moisture evaporation process.

• 설비공학논문집
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• 제27권3호
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• pp.146-151
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• 2015

The heat transfer performance of heating medium oil fluidized bed heat exchanger was measured. The operation variables were air flow rate, air inlet temperature, moisture content, water flow rate and water inlet temperature. The outside heat transfer coefficient was determined from the heat exchanger experiment and its experimental correlation was determined as a function of air velocity and viscosity of heating medium oil. Effect of viscosity was well agreed with the previous studies. Errors of the correlation equation was less than about 10% for outside heat transfer coefficient developed in this study when compared with the measured value. Hot water with the temperature greater than $77^{\circ}C$ could be produced by using the heating medium oil fluidized bed heat exchanger.

• Journal of Mechanical Science and Technology
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• 제14권5호
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• pp.537-546
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• 2000

The heat transfer characteristics of refrigerant-oil mixture for horizontal in-tube evaporator have been investigated experimentally. A smooth copper tube and a micro-fin tube with nominal 9.5 mm outer diameter and 1500 mm length were tested. For the pure refrigerant flow, the dependence of the axial heat transfer coefficient on quality was weak in the smooth tube, but in the micro-fin tube, the coefficients were 3 to 10 times greater as quality increases. Oil addition to pure refrigerant in the smooth tube altered the flow pattern dramatically at low mass fluxes, with a resultant enhancement of the wetting area by vigorous foaming. The heat transfer coefficients of the mixture for low and medium qualities were increased at low mass fluxes. In the micro-fin tube, however, the addition of oil deteriorates the local heat transfer performance for most of the quality range, except for low quality. The micro-fin tube consequently loses its advantage of high heat transfer performance for an oil fraction of 5%. Results are presented as plots of local heat transfer coefficient versus quality.

• 한국응용과학기술학회지
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• 제37권1호
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• pp.83-90
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• 2020

판형 열교환기는 1920년대부터 본격적으로 상업화되었으며, 이후 판형 열교환기의 기본 컨셉은 지금까지도 거의 변화가 없었지만 고온, 고압 그리고 대용량 열교환에 적용되기 위해 설계 및 제작 방법들이 혁신적으로 발전하여 지금에 이르게 되었다. 판형 열교환기의 개발 트렌드는 전열 효율이 좋으면서 압력강하가 낮고 또한 유체 분배가 잘되는 전열판의 개발과 일치한다. 본 연구에서는 이러한 트렌드를 만족시키는 선박용 중속엔진 오일 냉각용 판형 쿨러 개발과 관련된 주요 과정들을 소개하고, 또한 개발된 판형 오일쿨러의 전열성능을 실험적으로 분석하여 이에 대한 결과를 제공하고자 한다. 본 연구에서 판형 쿨러는 구조적 특징으로 인해 직접 판벽 온도를 측정할 수 없어 수정된 Wilson Plot 방법을 응용하여 열전달계수를 구하였다. 오일-물 실험 전에 물-물 실험을 통해 우선 물측의 열전달계수와 압력강하량을 구하였고, 그 결과를 바탕으로 오일측의 열전달계수를 구하였다. 양측 모두 유량 증가에 따라 열전달 성능은 증가하였지만, 압력강하량도 동시에 증가하였다. 그리고 실험을 통해 본 연구에서 개발된 판형 오일쿨러가 개발목표치를 성공적으로 달성하였음을 확인할 수 있었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.699-702
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• 2008

This paper describes the numerical simulations in the cooling of the radiator in a distribution transformer. The aim of this work is the cooling optimization of the transformer by CFD simulations. A clear understanding of the cooling pattern in a radiator which is a main heat remover in the power transformer is essential for optimizing the radiator design increasing the thermal efficiency. In this paper we study the heat transfer and fluid flow in a 3-phase 400kVA transformer. The plate radiators of this transformer become wrinkled (corrugated radiator) and there are filled with transformer oil. The oil is circulated due to the natural convection driven by buoyancy effects through radiators so that the ultimate cooling medium is the surrounding air. In the design of transformers, it is of interest to minimize the cost and size of radiators. The obtained results show the temperature and flow distributions and the possibility to optimize the transformer with 3-dimensional CFD models using FLUENT.

• 설비공학논문집
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• 제13권2호
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• pp.80-87
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• 2001

Microencapsulated PCM particles are mixed with distilled water and utilized to evaluate its characteristics and performance as a thermal storage medium transporting heat. For the present study, tetradecane(C$_14H_30, T_m=5.5^{\circ}C$) is capsulated in the core with the melamine of its surface. The size of particles is well-controlled under 10${\mu}{\textrm}{m}$ in the way of in-situ polymerization with melamine-formaldehyde resin. For the experiment, the concentrations of slurries are prepared for 20wt%, 30wt%, and 40wt%. The results are compared with those of water and 100% tetradecane oil. The pure water and tetradecane start solidifying within 20 minutes after introducing cooling water into the thermal storage tank whose tank whose flow rates are varied by 125cc/min, 250cc/min, and 500cc/min. However, MicroPCM slurries are required relatively longer period of time for their phase change than pure phase change materials. That is, the entrained MicroPCM particles control its heat transfer in terms of natural convection and conducting to them.

• 한국농업기계학회:학술대회논문집
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• 한국농업기계학회 2000년도 THE THIRD INTERNATIONAL CONFERENCE ON AGRICULTURAL MACHINERY ENGINEERING. V.III
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• pp.654-661
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• 2000

Area of greenhouse increases rapidly up to 45,265ha by the year of 1998 in Korea. Hot air heater with light oil combustion is the most common heater for greenhouse heating in the winter season. However, exhaust gas heat discharged to atmosphere through chimney reaches up to 10~20% of total heat of the oil combusted in the furnace. In order to recapture the heat of this exhaust gas and to recycle for greenhouse heating, the heat pipe type exhaust heat recovery system was manufactured and tested in this experiment. The exhaust heat recovery system was made for space heating in the greenhouse. The system consisted of a heat exchanger made of heat pipes, ${\emptyset}15.88{\times}600mm$ located in the rectangular box of $600{\times}550{\times}330mm$, a blower and air ducts. The rectangular box was divided by two compartments where hot chamber exposed to exhaust gas in which heat pipes could pick up the heat of exhaust gas, and by evaporation of the heat transfer medium in the pipes it carries the heat to the cold compartment, then the blower moves the heat to greenhouse. The number of heat pipe was 60, calculated considering the heat exchange amount between flue gas and heat transfer capacity of heat pipe. The working fluid of heat pipe was acetone because acetone is known for its excellent heat transfer capacity. The system was attached to the exhaust gas path. According to the performance test it could recover 53,809 to 74,613kJ/hr depending on the inlet air temperature of 12 to $-12^{circ}C$ respectively when air flow rate $1,100\textrm{m}^3/hr$. The exhaust gas temperature left the heat exchanger dropped to $100^{circ}C$ from $270^{circ}C$ by the heat exchange between the air and the flue gas, the temperature difference was collected by the air and the warm air temperature was about $60^{circ}C$ at the air flow rate of $1,100\textrm{m}^3/hr$. This heat pipe type exhaust heat recovery system can reduce fuel cost by 10% annually according to the economic analysis.

• 한국수산과학회지
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• 제21권5호
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• pp.277-287
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• 1988

In this paper, the influence of heating medium on the thermal diffusivities of fish meat paste products was studied. Model products were heated in boiling water, saturated steam and soybean oil. The differences in temperature raise of the products were interpreted with Biot number of the products. Because of the large overall heat transfer coefficient of heating medium, the temperature raise of the products in boiling water and saturated steam was fast and the Biot number of the products could be recognized as infinite. But the temperature raise of the products in soybean oil was slow and the Biot number of the products was less than 50.

• 대한기계학회논문집B
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• 제38권11호
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• pp.915-924
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• 2014

항공기용 가스터빈 엔진에 있어서, 기어 어셈블리 및 전자장비에 사용되는 오일의 냉각을 위하여 열교환기가 사용되며 이를 Surface air-oil heat exchanger (SAOHE) 라고 한다. 이 열교환기는 엔진 팬 케이싱 내부에 설치되며 기어박스 시스템 및 전자장비로부터 바이패스 덕트 후류 쪽으로 열을 소산시킨다. 본 연구의 목적은 SAOHE 의 설계를 위한 효율적인 수치해석방법을 개발하는 것이다. SAOHE 설치에 따른 핀에서의 열공력학적 성능을 평가하기 위하여 다공성 모델을 활용한 2 차원 수치해석을 수행하였고, 열교환기 성능평가에 대해 시간 및 비용적으로 효과적인 1 차원 열유동 네트워크 프로그램을 개발하였다. 이 프로그램을 이용하여 열교환기의 압력강하 및 열전달 성능을 예측하였고, 1 차원 열유동 네트워크 프로그램을 검증하기 위해 2 차원 전산해석 결과 및 실험 결과와 비교하였다.

• 한국정보전자통신기술학회논문지
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• 제9권2호
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• pp.185-189
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• 2016

에너지 절약형 전열제품 개발은 유가상승에 따라 국가의 최대 현안으로 꼽히고 있다. 따라서 최근에는 이러한 문제점들을 대처하기 위해 전기를 이용한 난방장치에 대한 에너지의 효율적 사용측면에서 경제성과 안정성을 높이기 위한 지속적인 연구 연구개발이 이루어지고 있고, 특히 고성능 및 신기능 소재에 대한 기술개발이 활발히 이루어지고 있다. 본 논문은 에너지 전달특성이 우수한 전열제품 개발에 관한 것으로 고효율 유도가열 장치에 관한 연구이다. 유도가열은 전자유도현상을 이용한 것으로 기존의 전도나 대류와 같은 열전달 방식과는 전혀 다르게 중간매질이 없이 피가열물에 직접 흡수되어 열로 전환되므로 급속, 균일하게 가열시키는 특징을 가진다. 또한 고주파 유도가열은 다양한 구조 설계가 가능하므로 가열 발열체를 적절히 활용하면 피가열물만을 집중가열 하는 것이 가능하다.